STREAM CROSSING RULES STREAM CROSSING RULES EnvEnv--Wt Part 900Wt Part 900
Application from theApplication from the DOT PerspectiveDOT Perspective
NHPWA Annual MeetingNHPWA Annual Meeting November 16, 2011November 16, 2011
Bureau of Environment Stream Team
Kevin Nyhan, Senior Environmental [email protected]
Matt Urban, Environmental [email protected]
Christine Perron, Senior Environmental [email protected]
(603) 271-1553
Presentation Outline
1. Origin of the Rules and Introduction
2. Specifics on the Stream Crossing Rules
3. DOT Implementation
4. Sample DOT Projects
5. Questions
Origin of the Rules and Introduction
History
Process began in 2006
Army Corps of Engineers directive
NH Stream Crossing Guidelines
Rules Workgroup
Rules effective May 12, 2010
Why Stream Crossing Rules?
Nationwide movement
Rivers move water, sediment, debris and are home to aquatic organisms
Move from hydraulic-only designs to designs that accommodate sediment transport
Estimated 17,000 culverts in NH (3,000 active dams (approx.))
Enhance public safety by establishing standards to:
Lessen the risk of blockages/flooding/wash-outs
Preserve the functions and values of existing streams
Restore stream channels to a more natural state
Improve aquatic organism (AO) passage
Purpose of Rules
From Top-of-Bank to Top-of-Bank and everything in between
DES Jurisdiction (No Change)
Ordinary High Water
Top-of-Bank
“The bankfull stage corresponds to the discharge at which channel maintenance is the most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work that results in the average morphologic characteristics of channels.” (Dunne & Leopold 1978)
The incipient elevation where flooding into a floodplain begins.
Bankfull Stage
Bankfull Stage
Bankfull Stage
Rivers form their banks and channel at the bankfull stage about every 1.5 years
Bankfull Stage
Bankfull
Bankfull Stage
Bankfull
Top-of-Bank
Ordinary High Water
Bankfull Stage
Normal Flow Bankfull Flow
Specifics of the Stream Crossing Rules
A ‘watercourse’ is a surface water that:
Develops and maintains a defined channel, with evidence of sediment transport, and
Is greater than 75’ in length, or is any length and connected to a wetland or other surface water at either end
Rules apply to “watercourses”
The crossing is located in a drainage swale, or ephemeral stream (only wet when it rains)
Rules do NOT apply, if…
The crossing qualifies for Routine Roadway Maintenance
Rules do NOT apply, if…
SB21 amended RSA 482-A:3,IV(b) so that… Man-made nontidal drainage ditches roadside and railroad ditches detention basins ponds and wetlands constructed to convey,
treat, or control stormwater and runoff erosional features caused by human activity
…may be maintained, repaired, replaced, or modified as necessary without a permit from DES.
You cannot impact any other jurisdictional area
As a matter of fact…
How do the stream rules apply?
General Design Considerations
All stream crossings shall:
Allow the movement of sediment & AO
Not increase freq. of flooding;
Maintain existing low flows;
Preserve/ restore watercourse connectivity;
Not cause water quality degradation
Not cause scour or aggradation
Tiers Based System: Contributing Watershed
USGS StreamStats
http://water.usgs.gov/osw/streamstats/new_hampshire.html
Tier 1
Contributing watershed less than 201 acres
Meet general design considerations
Accommodate 50-yr storm or other applicable reg.
Any type of structure (culvert/bridge);
Construct during low flow
Use BMPs during construction
Tier 1
Repair/rehabilitation available (explained later)
Compensatory mitigation not required, unless the general design considerations cannot be met, pursuant to the repair/rehabilitation section
Tier 2Contributing watershed from 201 ac - 639 ac
Specific design criteria (explained later)
Span structure (bridge), embedded pipe arch. open bottom culvert, embedded closed culvert
Stream simulation
Tier 2
In-kind replacement available (explained later)
Alternative design available (explained later)
Repair/rehabilitation available (explained later)
Plans stamped by a Professional Engineer
Construct during low flow
Use BMPs
Tier 2
Compensatory mitigation not required for:
Crossings that meet specific design criteria Repair/rehabilitated In-kind replacements
Tier 3
Contributing watershed greater than 639 ac
Designated river corridor (1/4 mile)
Impairments Benthic macroinvertebrate index Fish assemblage index Habitat assessments Stream channel stability
Tier 3100-year floodplain
Natural Heritage Bureau (NHB) record
Prime wetland or buffer
*Tier 3 Kick out (impairments, NHB record or 100-year floodplain)
Tier 3
Span structure (bridge), or open bottom culvert
Stream simulation
Alternative design available
Plans stamped by a Professional Engineer
Construct during low flow
Use BMPs
Tier 3
Compensatory mitigation not required for
Self-mitigating crossing Conforms to NH Stream Crossing Guidelines
Tier 2 & Tier 3 Design Criteria
NH Stream Crossing Guidelines
Water depth and flow in crossing same as natural channel
Vegetated banks on both sides of the watercourse for wildlife passage
Preserve natural alignment and grade of stream for natural flow and access to floodplain
Tier 2 & Tier 3 Design CriteriaAccommodate 100-year flood so that:
No increase in flood stages for abutters Sediment transport not negatively affected
Simulate a natural stream channel
Tier 1 & Tier 2 Repair/Rehabilitation
Can only be repaired/rehabilitated if the crossing does not have a history of causing or contributing to flooding
Concrete repair, slip lining, cured-in-place lining, concrete invert lining
Slipline shall only occur once
Tier 1 & Tier 2 In-Kind Replacement
Can only be repaired/rehabilitated if the crossing does not have a history of causing or contributing to flooding
Replacement is same size as existing or an upgrade (closed bottom culvert to an open bottom culvert)
Meet general design considerations
Not diminish hydraulic capacity
Not diminish aquatic organism passage, OR
Tier 1 & Tier 2 In-Kind Replacement
Replacement does not adversely affect stream channel, or stream bank stability; and
Not cause an increase in flooding or overtopping of banks
Could require compensatory mitigation
Replacing Tier 3 Crossings
Comply with design criteria for Tier 2 & Tier 3 crossings
Alternative design allowed
Alternative Designs If installing the structure required by rule is not “practicable,” propose an alternative
Written request accompanied by a “technical report”
Alternative Designs New/replacement Tier 2 & Tier 3 Crossings
Technical report demonstrates that adhering to the rules is not practicable
Meets specific design criteria to “maximum extent practicable”
Meets general design considerations
Alternative Designs
New/replacement Tier 1 Crossing
Technical report demonstrates that adhering to the rules is not practicable
Meets general design considerations to “maximum extent practicable”
Practicable
“Practicable means available and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall project purposes.” (Env-Wt 101.73)
DOT Implementation
Information at Crossing
Estimating Bankfull Conditions Flow Area Width Depth
2005 Regional Hydraulic Geometry Curves (provisional)
Reference Reach Bankfull width & bankfull depth
Entrenchment ratio
Sinuosity
Floodprone width
Longitudinal profile
Cross sections
Pebble count
Reference Reach
Fluvial Geomorphic Report
Engineering / Hydraulics
Drainage calculations Drainage area Soil type 25-year, 50-year, 100-year flows
Hydraulic calculations Headwater Outlet water velocity
When is a Fluvial Geomorphic Assessment Required?
New Tier 2 Crossings
Tier 2 repair/rehabilitation where there is a flooding history
Tier 2 replacement where there is a flooding history
All new/replacement Tier 3 Crossings
Rehabilitation/Modification of Tier 2 & Tier 3 Crossings
Rules are silent on rehabilitation of Tier 3 crossings and modifications to Tiers 1, 2 & 3 crossings
Repair/rehabilitation of Tier 3 crossings need to comply with the General Design Considerations insofar as possible
Modifications use Alternative Design process
Rehabilitation/Modification of Tier 2 & Tier 3 Crossings
Redefine “replacement” or add a definition for “upgrade or improvement”
Define “modification”
Adopt rules for “modification of existing crossings,” and “rehabilitation of Tier 3 crossings.”
Information Required for Stream Crossing Application
Dewatering system Flow estimates Diversion dam and sump locations Backwater prevention methods Sediment treatment plan
Erosion and pollution controls
Construction Sequence
*Not available at the time of application
Information Required for Stream Crossing Application
Contractor-prepared and –submitted SWPPP
Conditioned permits subject to review and approval by DES
DOT working toward supplying this information in advance for project development
Conditions
Personnel
Detail of data
How Long Does It Take?
For an average wadable Tier 2/3 stream…
3 hrs. to complete pre-survey review 24 hrs. to survey crossing & reference reach 10 hrs. to crunch & input data into CAD/D 3 hrs. to generate a report for Design Does not include hydraulic/drainage calculations
How Long Does It Take?
Nothing from NH Stream Crossing Guidelines
Wolman Pebble Count
Cross Section Analysis
Wetted Perimeter Cross-Section Analysis
Pebble Counts
Pebble Counts
Tier 1 stream crossing shall accommodate the greater of the 50-year frequency flood or other applicable standard
Tier 2/3 stream crossing shall accommodate the 100-year frequency flood
Accommodate does NOT mean “pass through the structure without headwater conditions.”
What Does “Accommodate” Mean?
It means you know where the flood water will go, and your design has taken it into consideration…
Roadside ditches Backwater onto adjacent land Over the road (which has been hardened) Overflow culvert Floodplain culvert Under or through the structure
What Does Accommodate Mean?
What Does Accommodate Mean?
Tier 2 & 3 crossings shall provide… “a vegetated bank on both sides of the watercourse to allow for wildlife passage.”
Vegetated Banks
Tier 2 & 3 crossings shall provide… “a vegetated bank on both sides of the watercourse to allow for wildlife passage.”
Vegetated Banks
Academic community, Dr. Ballestero, UNH, indicated rules for freshwater only
DES applies rules to saltwater systems
Saltwater Systems
DOT Stream Crossing Projects
Swanzey Bridge 150/056 (Tier 3 Modification)
Existing Tier 3 concrete slab bridge, 25’ wide
Watershed: 5,500 ac (8.6 sm)
Project to widen bridge to facilitate rehabilitation (traffic control)
Swanzey Bridge 150/056
Swanzey Bridge 150/056
Specifics (reference reach):
Field Collected Calculated (for info.) Wbf = 26.0’ Wbf = 35.7’ Dmaxbf = 2.4’ Dmaxbf = 2.3’
Technical report (qualitative), no fluvial geomorphic assessment required
Alternative design
Swanzey Bridge 150/056
Wakefield, Farnham Brook (Flooding History vs. No Flooding History)
Existing Tier 2 concrete box culvert 3’ H x 6’ W
Project proposed to replace the culvert
No flooding history
Wakefield, Farnham Brook
Wakefield, Farnham Brook
At Crossing:
Field Collected Wbf = 16.2’ Dmaxbf = 3.3’
Reference reach:
Field Collected Calculated (for info.) Wbf = 8.9’ Wbf = 12.4’ Dmaxbf = 0.7’ Dmaxbf = 1.3’
Wakefield, Farnham Brook
“In-kind replacement or upgrade” Proposed 3’ X 8’ box (embedded 1’)
However, if there were a flooding history: Stream Crossing Design Guidelines
Span: 1.2 X Wbf + 2’ or 14-foot span, or open bottomed or embedded culvert based on reference reach…essentially A BRIDGE
Wakefield, Farnham Brook
Stratham, Jewell Hill Brook (Saltwater Stream Crossing)
Existing 42’L x 66” dia. Tier 3 pipe arch
Tidal river
Stratham, Jewell Hill Brook
Crossing outlet: Field Collected
Wbf = 24.8’ Dmaxbf = 4.0’
Reference reach: Field Collected Calculated (for info.)
Wbf = 25.4’ Wbf = 14.2’ Dmaxbf = 6.8’ Dmaxbf = 1.4’
Stratham, Jewell Hill Brook
Proposed 40’ L X 8’ dia. plastic pipe embedded 18”
Waiver of stream crossing rules included NH Coastal Program (DES) suggested that rules should not apply to tidal streams
Alternative Design
Stratham, Jewell Hill Brook
Pinkham’s Grant, Ellis River (Watershed Size Estimate)
Pinkham’s Grant, Ellis RiverExisting 16.8’ span Tier 2 bridge
No flooding history
Pinkham’s Grant, Ellis River
Crossing outlet: Field Collected
Wbf = 14.7’ Dmaxbf = 1.8’
Reference reach Field Collected Calculated (for info.)
Wbf = 23.9’ Wbf = 10.4’ Dmaxbf = 2.2’ Dmaxbf = 1.2’
Pinkham’s Grant, Ellis River
Pinkham’s Grant, Ellis River
Pinkham’s Grant, Ellis RiverProposed 20’ span bridge
Replacement / upgrade of existing Tier 2
Fully compliant with rules
Courtesy of AEWC
Pinkham’s Grant, Ellis RiverUnder construction now
Courtesy of AEWC
North Hampton, Winnicut River (Wide Channel w/ Vegetation)
North Hampton, Winnicut RiverEmergent wetland adjacent to flowing water
Elevation of ground surface at the boundary between the wetland and the open water
Grasses mark decrease in flow velocity of moving water
- Shane Csiki, DES
North Hampton, Winnicut River
Northwood, Narrows Brook (Alternative Reference Reach)
Northwood, Narrows BrookExisting 5’ corrugated metal pipe arch, Tier 3
8 square mile watershed
Calculated Wbf = 36’
Northwood, Narrows BrookConvergence of two streams (Kelsey Brook andNarrows Brook
Northwood, Narrows BrookUpstream reference reach was vastly differentthan stream at crossing
Northwood, Narrows BrookKelsey Brook reference reach
CollectedReference Reach
Crossing
Northwood, Narrows Brook
Similar watershed area
Similar geographic location
Similar topographic location
Similar substrate material
Similar vegetative conditions
Similar stream gradient
To Date…
2-Tier 3 Replacement 2-Tier 3 Repair / modification 3-Tier 2 In-kind replacement / upgrade 1-Tier 1 Repair / rehabilitation 3-Tier 1 In-kind replacement / upgrade 1-Tier 1 Repair / modification
16 Assessments in 2010 13 Assessments in 2011
